Comprehensions & generators
List/dict/set comprehensions, generator expressions, and lazy iteration.
Batch Rows in Chunks with a Generator in Python
Group a list of row dicts into fixed-size chunks using a generator that yields one slice per call.
from typing import Iterator, List
def batch_rows(rows: List[dict], batch_size: int) -> Iterator[List[dict]]:
for i in range(0, len(rows), batch_size):
yield rows[i:i + batch_size]
if __name__ == "__main__":
sample_rows = [
{"id": 1, "name": "Alice"},
{"id": 2, "name": "Bob"},
…Convert Data in Python with Comprehensions and Generators
Convert mixed data to integers, filter and transform numbers, and extract fields from dicts using list comprehensions and generator expressions.
def convert_numbers(data):
"""Convert a list of mixed values into integers using a comprehension."""
return [int(item) for item in data if item is not None]
def double_even_numbers(numbers):
"""Double only even numbers using a generator expression."""
return (n * 2 for n in numbers if n % 2 == 0)
d…Count Data in Python with Comprehensions and Generators
Count list items with a dict comprehension and generate squares lazily with a generator expression, printing both results.
from collections import Counter
data = ["apple", "banana", "apple", "cherry", "banana", "apple"]
counts = {item: data.count(item) for item in set(data)}
square_gen = (x * x for x in range(5))
squares = list(square_gen)
if __name__ == "__main__":
print("Manual count:", counts)
print("Counter:", dict(Counter…Dict Comprehension to Map Keys to Lengths in Python
Build a dictionary that maps each word to its character count using a dictionary comprehension.
words = ["apple", "banana", "cherry", "date", "elderberry"]
word_lengths = {word: len(word) for word in words}
print(word_lengths)Generate Data with Python Comprehensions and Generators
Shows list, dict compregensions and generator expressions plus a Fibonacci generator to produce data lazily.
# Data generation helpers using comprehensions and generators
from itertools import islice
def fibonacci(limit):
"""Generate Fibonacci numbers up to a limit."""
a, b = 0, 1
while a <= limit:
yield a
a, b = b, a + b
def main():
# List comprehension: squares of even numbers
square…How to Group Data in Python with defaultdict and Comprehensions
Group a list of items by a computed key using a defaultdict-based generator helper and an alternative dictionary comprehension approach.
from collections import defaultdict
def group_by(data, key_func):
"""Group items in data by the value returned by key_func."""
result = defaultdict(list)
for item in data:
result[key_func(item)].append(item)
return dict(result)
def group_by_comprehension(data, key_func):
"""Same grouping …How to Parse CSV Rows as Generator Dicts in Python
Reads a CSV file and yields each row as a dictionary one at a time using a generator, so the file is processed lazily.
import csv
from pathlib import Path
def csv_to_dicts(filepath):
with open(filepath, mode="r", newline="", encoding="utf-8") as file:
reader = csv.DictReader(file)
for row in reader:
yield row
if __name__ == "__main__":
sample_csv = Path("sample_data.csv")
sample_csv.write_text…How to Parse Data with Generators and Comprehensions in Python
This code demonstrates using a generator expression to filter active users and a dictionary comprehension to aggregate scores by name.
def parse_data_helper(raw_records):
"""Extract active users' names and scores from raw records."""
parsed = (
(record["name"], record["score"])
for record in raw_records
if record["active"] and record["score"] >= 0
)
return list(parsed)
def aggregate_scores(parsed_data):
"…How to Use Comprehensions and Generators in Python
Demonstrate list, set, and dictionary comprehensions plus generator expressions and generator functions in one beginner-friendly script.
def demonstrate_comprehensions_generators():
# List comprehension: transform and filter in one line
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
squares = [num ** 2 for num in numbers if num % 2 == 0]
print(f"Square of even numbers (list comprehension): {squares}")
# Set comprehension: unique values
…How to Use Comprehensions and Generators to Check Data in Python
A beginner-friendly helper that filters numeric values, computes squares and cubes with comprehensions and a generator, and returns a summary dictionary.
def check_data(iterable):
"""Return a summary of numeric data using comprehensions and a generator."""
values = [item for item in iterable if isinstance(item, (int, float))]
squares = [x ** 2 for x in values if x > 0]
cubes = (x ** 3 for x in values if x > 0)
cube_list = list(cubes)
return {
…How to Use List Comprehensions and Generators to Format Data in Python
A beginner-friendly helper that formats dictionaries into strings using a list comprehension and generates squared numbers lazily with a generator.
def format_data(items):
"""Format a list of dictionaries into readable strings."""
formatted = [
f"{item.get('name', 'Unknown')}: {item.get('value', 0)} units"
for item in items
if item.get('value', 0) > 0
]
return formatted if formatted else ["No positive values found"]
def g…How to Validate Data with Python Comprehensions and Generators
Use list, generator, and dictionary comprehensions to filter and transform data for quick validation in Python.
def validate_integer(data):
return [item for item in data if isinstance(item, int)]
def validate_positive(numbers):
return (num for num in numbers if num > 0)
def validate_string_lengths(data, min_length=3):
return {item: len(item) for item in data if isinstance(item, str) and len(item) >= min_length}
i…Merge Data with Comprehension and Generator in Python
Merge user and order data using a dictionary comprehension for lookups and a generator expression to filter and transform orders.
def merge_data(users, orders):
"""
Merge user and order data using a dictionary comprehension
and a generator expression for filtering.
"""
# Build a lookup: user_id -> user name
user_map = {user["id"]: user["name"] for user in users}
# Generator: yield orders with user names attached
…Python Comprehensions and Generators for Beginners
Learn list, dict, and set comprehensions plus generator expressions and generator functions with clear, runnable examples.
# Demonstrates list comprehensions, dict comprehensions, set comprehensions, and generators
def demonstrate_comprehensions():
# List comprehension: squares of even numbers
numbers = range(1, 11)
even_squares = [n ** 2 for n in numbers if n % 2 == 0]
# Dict comprehension: number to its factorial
…Write Data Helpers with Comprehensions and Generators in Python
Demonstrates list, dict, and set comprehensions plus generator expressions and generator functions for building concise data helpers.
# Basic comprehensions and generators demo
# List comprehension: squares of evens
squares = [x * x for x in range(10) if x % 2 == 0]
print("List comp:", squares)
# Dictionary comprehension: char -> count
text = "hello"
char_counts = {c: text.count(c) for c in set(text)}
print("Dict comp:", char_counts)
# Set compre…Browse by section
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Comprehensions & generators — Python code examples
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This page collects comprehensions & generators snippets — short, copy-ready Python you can paste into our free online IDE and run without installing anything. Each sample includes a plain-English explanation and the full source code.
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